Process for purifying 1,1,1,5,5,5-hexafluoroacetylacetone

ABSTRACT

The invention relates to a process for purifying a crude 1,1,1,5,5,5-hexafluoroacetylacetone. This process includes (a) hydrating the crude 1,1,1,5,5,5-hexafluoroacetylacetone to a 1,1,1,5,5,5-hexafluoroacetylacetone hydrate; and (b) dehydrating the 1,1,1,5,5,5-hexafluoroacetylacetone hydrate, thereby obtaining a purified 1,1,1,5,5,5-hexafluoroacetylacetone. Prior to the step (b), the 1,1,1,5,5,5-hexafluoroacetylacetone hydrate may be brought into contact with a poor solvent in which 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate is substantially insoluble. Furthermore, the step (a) may be conducted in a poor solvent in which 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate is substantially insoluble. It is possible by the process to easily obtain 1,1,1,5,5,5-hexafluoroacetylacetone with high purity.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a process for producing1,1,1,5,5,5-hexafluoroacetylacetone with high purity, which is useful asan intermediate for producing medicines, agricultural chemicals andelectric parts.

[0002] H. Gilman et al., J. Am. Chem. Soc., Vol. 78, pp. 2790-2792(1956) teaches a process for producing1,1,1,5,5,5-hexafluoroacetylacetone, which is shown by the followingreaction formulas:

[0003] A. Henne et al., J. Amer. Chem. Soc., Vol. 69, pp. 1819-1820(1947) discloses a process for producing anhydrous1,1,1,5,5,5-hexafluoroacetylacetone by turning a sodium salt of1,1,1,5,5,5-hexafluoroacetylacetone into a copper chelate compound, thenrecrystallizing the copper chelate compound, and then removing thecopper with hydrogen sulfide.

[0004] R. Haszeldine et al., J. Chem. Soc. London, 1951, pp. 609-612discloses that a reaction liquid is treated with dilute sulfuric acidand then extracted with ether, and the resulting organic layer isdistilled to obtain distillates over the range 36-90° C. It is disclosedtherein that the portion of boiling point 85-90° C. appears to be1,1,1,5,5,5-hexafluoroacetylacetone dihydrate.

[0005] H. Gilman et al., J. Am. Chem. Soc., Vol. 78, pp. 2790-2792(1956) further discloses the precipitation of1,1,1,5,5,5-hexafluoroacetylacetone dihydrate by concentrating anorganic layer extracted with ether.

[0006] In general, raw materials, including1,1,1,5,5,5-hexafluoroacetylacetone, for producing medicines,agricultural chemicals and electronic parts are required to have higherpurity, as compared with raw materials for other uses.

SUMMARY OF THE INVENTION

[0007] It is therefore an object of the present invention to provide aprocess for purifying a crude 1,1,1,5,5,5-hexafluoroacetylacetone.

[0008] According to the present invention, there is provided a processfor purifying a crude 1,1,1,5,5,5-hexafluoroacetylacetone. This processcomprises (a) hydrating said crude 1,1,1,5,5,5-hexafluoroacetylacetone;and (b) dehydrating a product of said hydrating, thereby obtaining apurified 1,1,1,5,5,5-hexafluoroacetylacetone.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] It is possible by the process to easily obtain1,1,1,5,5,5-hexafluoroacetylacetone with high purity.

[0010] Since 1,1,1,5,5,5-hexafluoroacetylacetone is superior as asolvent or chelating agent, it may contain various impurities. Some ofthese impurities can be removed or decreased by distillation, but otherimpurities can not. According to the invention, however, it is possibleto highly purify a crude 1,1,1,5,5,5-hexafluoroacetylacetone by removingeven such other impurities.

[0011] The raw material of the step (a) in the process, a crude1,1,1,5,5,5-hexafluoroacetylacetone, is not particularly limited, aslong as it contains impurities dissolved or dispersed therein. Theimpurities may be organic matters, inorganic matters, and/or acombination of these. Their content is not limited, either. If the crude1,1,1,5,5,5-hexafluoroacetylacetone contains a solid matter asimpurities, it is preferable to remove it by filtration. This removalis, however, not necessarily required depending on the treatmentconditions of the process.

[0012] The step (a) of the process can be conducted by charging areaction vessel with 1 part by mole of a crude1,1,1,5,5,5-hexafluoroacetylacetone and 2 parts by mole or greater(preferably 2 to about 50 parts by moles, more preferably 2 to about 30parts by mole) of water for hydrolyzing the crude1,1,1,5,5,5-hexafluoroacetylacetone. According to need, it is possibleto add an acid (e.g., sulfuric acid, hydrochloric acid and nitric acid)to the reaction vessel and/or to increase the temperature of thereaction vessel in order to accelerate the hydration. It is estimatedthat a 1,1,1,5,5,5-hexafluoroacetylacetone hydrate is produced by thestep (a). If an excessive amount of water is used in the step (a), theproduct of the step (a) is obtained in the form of an aqueous solution.In this case, it is possible to extract the product of the step (a) witha solvent in which a 1,1,1,5,5,5-hexafluoroacetylacetone hydrate issoluble, thereby obtaining an organic layer, and then to remove thissolvent from the organic layer, thereby obtaining the1,1,1,5,5,5-hexafluoroacetylacetone hydrate in the form of solid. Thishydrate is usually 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate[CF₃C(OH)₂CH₂C(OH)₂CF₃], but may be another hydrate other than dihydrateor a mixture of these hydrates. The obtained1,1,1,5,5,5-hexafluoroacetylacetone hydrate may be dried, but the dryingis not necessarily required if this hydrate is used as a raw materialfor producing 1,1,1,5,5,5-hexafluoroacetylacetone (anhydride).Dehydration of the 1,1,1,5,5,5-hexafluoroacetylacetone hydrate leads tothe obtainment of 1,1,1,5,5,5-hexafluoroacetylacetone. Furthermore, itis optional to conduct a distillation or contact with a solid adsorbent(e.g., zeolite, alumina and silica gel) in order to further purify theobtained 1,1,1,5,5,5-hexafluoroacetylacetone.

[0013] It is possible to dehydrate a 1,1,1,5,5,5-hexafluoroacetylacetonehydrate by a conventional method, thereby obtaining its anhydride. R.Belford, J. Inorganic and Nuclear Chemistry, 1956, Vol. 2, pp. 11-31discloses such method in which a dispersion is prepared by shaking1,1,1,5,5,5-hexafluoroacetylacetone dihydrate with approximately threetimes its volume of 98% sulfuric acid. After the dispersion has beenallowed to stand overnight, dehydration of the product is repeated witha fresh batch of sulfuric acid. The resulting upper layer is siphonedoff and distilled, thereby obtaining the anhydride (yield: 98%) as adistillate between 70.0-70.2° C. J. Amer. Chem. Soc., 78, 2790 (1956)discloses another method in which anhydrous calcium sulfate is mixedwith 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate. Then, the resultingmixture is heated. The distillate is again treated with anhydrouscalcium sulfate and distilled, thereby obtaining the anhydride of aboiling point of 68° C. (736 mm.). There is known a still another methodin which 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate, together withphosphorus pentoxide, is heated in ether.

[0014] In the invention, the hydration of the step (a) may be conductedat a temperature of about 0-90° C., preferably about 20-70° C. If it islower than 0° C., the reaction rate may become too low. If it is higherthan 90° C., the yield of the 1,1,1,5,5,5-hexafluoroacetylacetonehydrate may become too low.

[0015] The above-mentioned extracting solvent, in which a1,1,1,5,5,5-hexafluoroacetylacetone hydrate is soluble, can be selectedfrom ethers and halogen-containing solvents. This solvent is naturallyin the form of liquid upon its use. Its boiling point is notparticularly limited, but is preferably about 100° C. or lower. Examplesof the ethers are diethyl ether, diisopropyl ether, diisobutyl ether,dibutyl ether, t-butyl methyl ether, tetrahydrofuran, anisole, anddioxane. Examples of the halogen-containing solvents are methylenechloride, chloroform, carbon tetrachloride, 1,2-dichloroethane,1,2-bis(trifluoromethyl)benzene, 1,3-bis(trifluoromethyl)benzene,1,4-bis(trifluoromethyl)benzene, and 2,4-dichlorobenzotrifluoride. Ofthese, the ethers are preferable. Furthermore, t-butyl methyl ether isparticularly preferable.

[0016] In the invention, it is possible by the step (a) to obtain acrude 1,1,1,5,5,5-hexafluoroacetylacetone hydrate. Prior to thedehydration, it is preferable to bring the crude1,1,1,5,5,5-hexafluoroacetylacetone hydrate into contact with a poorsolvent in which 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate issubstantially insoluble. With this, impurities are more remarkablyremoved from the crude 1,1,1,5,5,5-hexafluoroacetylacetone hydrate. Theway of bringing it into contact with the poor solvent is notparticularly limited. For example, it is possible to disperse the crude1,1,1,5,5,5-hexafluoroacetylacetone hydrate in the poor solvent. Then,the precipitated 1,1,1,5,5,5-hexafluoroacetylacetone hydrate can beseparated by filtration. As another example, it is possible to apply thepoor solvent as a washing liquid to the crude1,1,1,5,5,5-hexafluoroacetylacetone hydrate.

[0017] The above-mentioned poor solvent can be selected fromhydrocarbons and fluorine-containing solvents free from chlorine. It isneedless to say that this poor solvent is in the form of liquid upon itsuse. This poor solvent is not particularly limited, and its boilingpoint is preferably not higher than about 200° C. Examples of thehydrocarbons are (1) aliphatic hydrocarbons such as n-pentane, n-hexane,n-heptane, n-octane, n-nonane, n-decane and isomers of these, theisomers being in liquid at about 5° C.; (2) aromatic hydrocarbons suchas benzene, toluene, o-xylene, m-xylene, p-xylene, ethyl benzene, andmesitylene; (3) alicyclic hydrocarbons such as cyclopentane,cyclohexane, methylcyclopentane, methylcyclohexane, tetralin, anddecalin; and (4) industrial gasolines (mixtures of hydrocarbon solvents)such as ligroin and petroleum ether. Examples of the fluorine-containingsolvents are 1,2-bis(trifluoromethyl)benzene,1,3-bis(trifluoromethyl)benzene, 1,4-bis(trifluoromethyl)benzene,1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane,heptafluorocyclopentane, and perfluorinated cyclic ethers (FLORINAT®).It is possible to use a mixture of at least two of these.

[0018] It is optional to mix the poor solvent with a small amount of agood solvent in which solubility of 1,1,1,5,5,5-hexafluoroacetylacetonedihydrate is higher than in the poor solvent. The amount of the goodsolvent may be not greater than 30 parts by weight per 100 parts byweight of the poor solvent. The good solvent in the invention is notparticularly limited. Its examples are ethers such as diethyl ether,dibutyl ether, t-butyl methyl ether, diisopropyl ether, andtetrahydrofuran (THF); and alcohols such as methanol, ethanol,n-propanol, isopropanol, and n-butanol.

[0019] The temperature for bringing the crude1,1,1,5,5,5-hexafluoroacetylacetone hydrate with the poor solvent is notparticularly limited. It is preferably about 0-90° C., more preferablyabout 20-60° C. In view of operability, it is preferably a temperaturerequiring no heating nor cooling.

[0020] In the invention, the hydration can also be conducted in the poorsolvent by adding 2 parts by mole or greater of water to 1 part by moleof the crude 1,1,1,5,5,5-hexafluoroacetylacetone. In this hydration, itis preferable to use water in an amount of about 2-10 moles, morepreferably about 2-7 moles, still more preferably about 2-5 moles, permole of the crude 1,1,1,5,5,5-hexafluoroacetylacetone. The1,1,1,5,5,5-hexafluoroacetylacetone hydrate obtained by this hydrationis almost in the form of solid, since the hydration is conducted in thepoor solvent. Even in this hydration, an aqueous layer may be formed byadding an excessive amount of water. In this case, the1,1,1,5,5,5-hexafluoroacetylacetone hydrate is partially dissolved inthe aqueous layer. It is, however, possible to collect such hydrate byextracting the aqueous layer with the above-mentioned extractingsolvent. After the hydration, it is possible to obtain a1,1,1,5,5,5-hexafluoroacetylacetone hydrate in the form of solid(crystals) by removing the poor solvent by concentration or filtration.The resulting 1,1,1,5,5,5-hexafluoroacetylacetone hydrate (dihydrate)can be dehydrated into the target 1,1,1,5,5,5-hexafluoroacetylacetone.Prior to this dehydration, it is optional to bring this hydrate intocontact with the poor solvent.

[0021] In the invention, it is preferable to use a reaction vessel madeof glass, fluororesin, or a material lined with one of these.

[0022] The following nonlimitative examples are illustrative of thepresent invention.

EXAMPLE 1

[0023] A 200-liter glass-lined reaction vessel, equipped with athermoelectric thermometer and a stirrer, was charged with 33.0 kg of acrude 1,1,1,5,5,5-hexafluoroacetylacetone, 49.0 kg of water, and 1.7 kgof 98% sulfuric acid. This crude hexafluoroacetylacetone was found tohave a purity of 97.0% by a gas chromatography (detector: FID, column:DB-1, column size: 0.25 mm×60 m). The reaction was conducted for 6 hr,while the reaction mixture was maintained at 60° C. After the reaction,the reaction liquid was cooled down to about 20° C., followed byextraction with 62.0 kg of t-butyl methyl ether. The resulting aqueouslayer was extracted again with 12.7 kg of t-butyl methyl ether. Theresulting two organic layers were combined together, followed bydistilling t-butyl methyl ether off. To the obtained crude1,1,1,5,5,5-hexafluoroacetylacetone dihydrate 60.0 kg of toluene wereadded, followed by stirring for 2 hr at a liquid temperature of 15-20°C. The resulting crystals were separated by centrifugation, filtrationand vacuum drying with a vibrating dryer, thereby obtaining 31.9 kg of1,1,1,5,5,5-hexafluoroacetylacetone dihydrate. Then, a 200-literglass-lined reaction vessel, equipped with a thermoelectric thermometerand a stirrer, was charged with 31.9 kg of the obtained1,1,1,5,5,5-hexafluoroacetylacetone dihydrate and 63.8 kg of 98%sulfuric acid, followed by stirring for 4 hr at a temperature of 15-20°C. Then, the reaction liquid was allowed to stand still for 1 hr to havetwo layers separated from each other. Then, 23.8 kg of1,1,1,5,5,5-hexafluoroacetylacetone were obtained by distillation fromthe organic layer. This product was found by the gas chromatography tobe 1,1,1,5,5,5-hexafluoroacetylacetone having a purity of 99.9% (areal %in gas chromatography).

EXAMPLE 2

[0024] A 200-liter glass-lined reaction vessel, equipped with athermoelectric thermometer and a stirrer, was charged with 33.0 kg of acrude 1,1,1,5,5,5-hexafluoroacetylacetone (purity: 97.0%), 100 kg oftoluene, 8.5 kg of water, and 0.09 kg of 98% sulfuric acid. The reactionwas conducted for 5 hr, while the reaction mixture was maintained at 60°C. After the reaction, the reaction liquid was cooled down to about 20°C. The resulting crystals were separated by centrifugation, filtrationand vacuum drying with a vibrating dryer, thereby obtaining 31.0 kg of1,1,1,5,5,5-hexafluoroacetylacetone dihydrate. Then, a 200-literglass-lined reaction vessel, equipped with a thermoelectric thermometerand a stirrer, was charged with 31.0 kg of the obtained1,1,1,5,5,5-hexafluoroacetylacetone dihydrate and 62.0 kg of 98%sulfuric acid, followed by stirring for 4 hr at a temperature of 15-20°C. Then, the reaction liquid was allowed to stand still for 1 hr to havetwo layers separated from each other. Then, 24.2 kg of1,1,1,5,5,5-hexafluoroacetylacetone were obtained by distillation fromthe organic layer. This product was found by the gas chromatography tobe 1,1,1,5,5,5-hexafluoroacetylacetone having a purity of 99.9%.

EXAMPLE 3

[0025] A 200-liter glass-lined reaction vessel, equipped with athermoelectric thermometer and a stirrer, was charged with 33.0 kg of acrude 1,1,1,5,5,5-hexafluoroacetylacetone (purity: 97.0%), 100 kg oftoluene, and 8.6 kg of water. The reaction was conducted for 5 hr, whilethe reaction mixture was maintained at 60° C. After the reaction, thereaction liquid was cooled down to about 20° C. The resulting crystalswere separated by centrifugation, filtration and vacuum drying with avibrating dryer, thereby obtaining 32.3 kg of1,1,1,5,5,5-hexafluoroacetylacetone dihydrate. Then, a 200-literglass-lined reaction vessel, equipped with a thermoelectric thermometerand a stirrer, was charged with 32.3 kg of the obtained1,1,1,5,5,5-hexafluoroacetylacetone dihydrate and 64.6 kg of 98%sulfuric acid, followed by stirring for 4 hr at a temperature of 15-20°C. Then, the reaction liquid was allowed to stand still for 1 hr to havetwo layers separated from each other. Then, 25.2 kg of1,1,1,5,5,5-hexafluoroacetylacetone were obtained by distillation fromthe organic layer. This product was found by the gas chromatography tobe 1,1,1,5,5,5-hexafluoroacetylacetone having a purity of 99.9%.

[0026] The entire disclosure of Japanese Patent Application No.2000-178891 filed on Jun. 14, 2000, including specification, claims andsummary, is incorporated herein by reference in its entirety.

What is claimed is:
 1. A process for purifying a crude1,1,1,5,5,5-hexafluoroacetylacetone, said process comprising: (a)hydrating said crude 1,1,1,5,5,5-hexafluoroacetylacetone; and (b)dehydrating a product of said hydrating, thereby obtaining a purified1,1,1,5,5,5-hexafluoroacetylacetone.
 2. A process according to claim 1,wherein said product of said hydrating comprises a1,1,1,5,5,5-hexafluoroacetylacetone hydrate.
 3. A process according toclaim 2, wherein said 1,1,1,5,5,5-hexafluoroacetylacetone hydrate is1,1,1,5,5,5-hexafluoroacetylacetone dihydrate.
 4. A process according toclaim 1, wherein said hydrating is conducted by adding 2 parts by moleor greater of water to 1 part by mole of said crude1,1,1,5,5,5-hexafluoroacetylacetone.
 5. A process according to claim 4,wherein said hydrating is conducted by further adding an acid to saidcrude 1,1,1,5,5,5-hexafluoroacetylacetone.
 6. A process according toclaim 1, wherein said hydrating is conducted at a temperature of from 0to 90° C.
 7. A process according to claim 1, wherein, prior to saiddehydrating, said process further comprises: (c) extracting said productof said hydrating with a solvent in which a1,1,1,5,5,5-hexafluoroacetylacetone hydrate is soluble, therebyobtaining an organic layer; and (d) removing said solvent from saidorganic layer, thereby obtaining a product comprising said1,1,1,5,5,5-hexafluoroacetylacetone hydrate.
 8. A process according toclaim 7, wherein said solvent has a boiling point of not higher thanabout 100° C.
 9. A process according to claim 7, wherein said solvent isat least one selected from the group consisting of ethers andhalogen-containing organic solvents.
 10. A process according to claim 9,wherein said ethers are diethyl ether, diisopropyl ether, diisobutylether, dibutyl ether, t-butyl methyl ether, tetrahydrofuran, anisole,and dioxane, wherein said halogen-containing organic solvents aremethylene chloride, chloroform, carbon tetrachloride,1,2-dichloroethane, 1,2-bis(trifluoromethyl)benzene,1,3-bis(trifluoromethyl)benzene, 1,4-bis(trifluoromethyl)benzene, and2,4-dichlorobenzotrifluoride.
 11. A process according to claim 9,wherein said solvent is t-butyl methyl ether.
 12. A process forpurifying a crude 1,1,1,5,5,5-hexafluoroacetylacetone, said processcomprising: (a) hydrating said crude1,1,1,5,5,5-hexafluoroacetylacetone, thereby obtaining a crude1,1,1,5,5,5-hexafluoroacetylacetone hydrate; (b) bringing said crude1,1,1,5,5,5-hexafluoroacetylacetone hydrate into contact with a poorsolvent in which 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate issubstantially insoluble, thereby obtaining a1,1,1,5,5,5-hexafluoroacetylacetone hydrate; and (c) dehydrating said1,1,1,5,5,5-hexafluoroacetylacetone hydrate into a purified1,1,1,5,5,5-hexafluoroacetylacetone.
 13. A process according to claim12, wherein said poor solvent has a boiling point of not higher thanabout 200° C.
 14. A process according to claim 12, wherein said poorsolvent is at least one selected from the group consisting of aromatichydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, industrialgasolines, and fluorine-containing solvents.
 15. A process according toclaim 14, wherein said aromatic hydrocarbons are benzene, toluene,o-xylene, m-xylene, p-xylene, ethyl benzene, and mesitylene, whereinsaid aliphatic hydrocarbons are n-pentane, n-hexane, n-heptane,n-octane, n-nonane, n-decane, and isomers thereof, each of said isomersbeing in a liquid at about 5° C., wherein said alicyclic hydrocarbonsare cyclopentane, cyclohexane, methylcyclopentane, methylcyclohexane,tetralin, and decalin, wherein said industrial gasolines are ligroin andpetroleum ether, wherein said fluorine-containing solvents are1,2-bis(trifluoromethyl)benzene, 1,3-bis(trifluoromethyl)benzene,1,4-bis(trifluoromethyl)benzene, 1,1,1,3,3-pentafluoropropane,1,1,1,3,3-pentafluorobutane, heptafluorocyclopentane, and perfluorinatedcyclic ethers.
 16. A process according to claim 12, wherein saidbringing is conducted by bringing said crude1,1,1,5,5,5-hexafluoroacetylacetone hydrate into contact with a mixtureof said poor solvent and a good solvent that is in an amount of notgreater than 30 parts by weight per 100 parts by weight of said poorsolvent, said good solvent being such that1,1,1,5,5,5-hexafluoroacetylacetone dihydrate has a higher solubility insaid good solvent than in said poor solvent.
 17. A process according toclaim 16, wherein said good solvent is at least one selected from thegroup consisting of ethers and alcohols.
 18. A process according toclaim 17, wherein each of said ethers has a boiling point of about30-140° C.
 19. A process according to claim 17, wherein said ethers arediethyl ether, dibutyl ether, t-butyl methyl ether, diisopropyl ether,and tetrahydrofuran.
 20. A process according to claim 17, wherein saidalcohols are methanol, ethanol, n-propanol, isopropanol, and n-butanol.21. A process for purifying a crude 1,1,1,5,5,5-hexafluoroacetylacetone,said process comprising: (a) hydrating said crude1,1,1,5,5,5-hexafluoroacetylacetone in a poor solvent in which1,1,1,5,5,5-hexafluoroacetylacetone dihydrate is substantiallyinsoluble, thereby obtaining a 1,1,1,5,5,5-hexafluoroacetylacetonehydrate; and (b) dehydrating said 1,1,1,5,5,5-hexafluoroacetylacetonehydrate into a purified 1,1,1,5,5,5-hexafluoroacetylacetone.
 22. Aprocess according to claim 21, wherein, prior to said dehydrating, said1,1,1,5,5,5-hexafluoroacetylacetone hydrate is brought into contact witha poor solvent in which 1,1,1,5,5,5-hexafluoroacetylacetone dihydrate issubstantially insoluble.